CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Treasury Stock
Balance at Dec. 31, 2018	$ 346,208	$ 154	$ 1,134,227	$ (610,482)	$ (177,691)
Balance (in shares) at Dec. 31, 2018		15,428,000			2,618,000
Increase (Decrease) in Stockholders' Equity
Net (loss) income and comprehensive (loss) income	(512)			(512)
Non-cash compensation	14,053		14,053
Purchase of treasury stock	(3,976)				$ (3,976)
Purchase of treasury stock (in shares)					18,000
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes	(3,585)	$ 1	(3,586)
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes (in shares)		87,000
Balance at Mar. 31, 2019	352,188	$ 155	1,144,694	(610,994)	$ (181,667)
Balance (in shares) at Mar. 31, 2019		15,515,000			2,636,000
Balance at Dec. 31, 2018	346,208	$ 154	1,134,227	(610,482)	$ (177,691)
Balance (in shares) at Dec. 31, 2018		15,428,000			2,618,000
Increase (Decrease) in Stockholders' Equity
Net (loss) income and comprehensive (loss) income	15,970
Purchase of treasury stock	$ (4,300)
Purchase of treasury stock (in shares)	18,580
Balance at Sep. 30, 2019	$ 389,264	$ 156	1,165,597	(594,512)	$ (181,977)
Balance (in shares) at Sep. 30, 2019		15,635,000			2,637,000
Balance at Mar. 31, 2019	352,188	$ 155	1,144,694	(610,994)	$ (181,667)
Balance (in shares) at Mar. 31, 2019		15,515,000			2,636,000
Increase (Decrease) in Stockholders' Equity
Net (loss) income and comprehensive (loss) income	12,218			12,218
Non-cash compensation	15,982		15,982
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes	(6,501)	$ 1	(6,502)
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes (in shares)		89,000
Balance at Jun. 30, 2019	373,887	$ 156	1,154,174	(598,776)	$ (181,667)
Balance (in shares) at Jun. 30, 2019		15,604,000			2,636,000
Increase (Decrease) in Stockholders' Equity
Net (loss) income and comprehensive (loss) income	4,264			4,264
Non-cash compensation	10,797		10,797
Purchase of treasury stock	(310)				$ (310)
Purchase of treasury stock (in shares)					1,000
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes	626		626
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes (in shares)		31,000
Balance at Sep. 30, 2019	389,264	$ 156	1,165,597	(594,512)	$ (181,977)
Balance (in shares) at Sep. 30, 2019		15,635,000			2,637,000
Balance at Dec. 31, 2019	402,326	$ 157	1,177,984	(592,654)	$ (183,161)
Balance (in shares) at Dec. 31, 2019		15,677,000			2,641,000
Increase (Decrease) in Stockholders' Equity
Net (loss) income and comprehensive (loss) income	14,401			14,401
Non-cash compensation	11,917		11,917
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes	(5,087)		(5,087)
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes (in shares)		27,000
Other	0	$ 0	(1)	1
Balance at Mar. 31, 2020	423,557	$ 157	1,184,813	(578,252)	$ (183,161)
Balance (in shares) at Mar. 31, 2020		15,704,000			2,641,000
Balance at Dec. 31, 2019	402,326	$ 157	1,177,984	(592,654)	$ (183,161)
Balance (in shares) at Dec. 31, 2019		15,677,000			2,641,000
Increase (Decrease) in Stockholders' Equity
Net (loss) income and comprehensive (loss) income	(39,999)
Balance at Sep. 30, 2020	361,009	$ 158	1,176,664	(632,652)	$ (183,161)
Balance (in shares) at Sep. 30, 2020		15,759,000			2,641,000
Balance at Mar. 31, 2020	423,557	$ 157	1,184,813	(578,252)	$ (183,161)
Balance (in shares) at Mar. 31, 2020		15,704,000			2,641,000
Increase (Decrease) in Stockholders' Equity
Net (loss) income and comprehensive (loss) income	(29,757)			(29,757)
Non-cash compensation	13,158		13,158
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes	(981)		(981)
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes (in shares)		27,000
Balance at Jun. 30, 2020	405,977	$ 157	1,196,990	(608,009)	$ (183,161)
Balance (in shares) at Jun. 30, 2020		15,731,000			2,641,000
Increase (Decrease) in Stockholders' Equity
Net (loss) income and comprehensive (loss) income	(24,643)			(24,643)
Non-cash compensation	14,161		14,161
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes	4,646	$ 1	4,645
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt	116,300		116,300
Issuance of common stock for stock options, restricted stock awards and restricted stock units, net of withholding taxes (in shares)		28,000
Repurchase of 0.625% Convertible Senior Notes, net	(107,882)		(107,882)
Convertible note hedge transactions	(14,379)		(14,379)
Warrant transactions	(33,171)		(33,171)
Balance at Sep. 30, 2020	$ 361,009	$ 158	$ 1,176,664	$ (632,652)	$ (183,161)
Balance (in shares) at Sep. 30, 2020		15,759,000			2,641,000